Comparison of thrombolysis versus surgery as a first line therapy for prosthetic heart valve thrombosis

Real-time three-dimensional transesophageal echocardiography in the assessment of mechanical prosthetic mitral valve ring thrombosis

Although 2-dimensional (2D) transesophageal echocardiography (TEE) is the gold standard for the diagnosis of prosthetic valve thrombosis, nonobstructive clots located on mitral valve rings can be missed. Real-time 3-dimensional (3D) TEE has incremental value in the visualization of mitral prosthesis. The aim of this study was to investigate the utility of real-time 3D TEE in the diagnosis of mitral prosthetic ring thrombosis. The clinical outcomes of these patients in relation to real-time 3D transesophageal echocardiographic findings were analyzed. Of 1,263 patients who underwent echocardiographic studies, 174 patients (37 men, 137 women) with mitral ring thrombosis detected by real-time 3D TEE constituted the main study population. Patients were followed prospectively on oral anticoagulation for 25 ± 7 months. Eighty-nine patients (51%) had thrombi that were missed on 2D TEE and depicted only on real-time 3D TEE. The remaining cases were partially visualized with 2D TEE but completely visualized with real-time 3D TEE. Thirty-seven patients (21%) had thromboembolism. The mean thickness of the ring thrombosis in patients with thromboembolism was greater than that in patients without thromboembolism (3.8 ± 0.9 vs 2.8 ± 0.7 mm, p <0.001). One hundred fifty-five patients (89%) underwent real-time 3D TEE during follow-up. There were no thrombi in 39 patients (25%); 45 (29%) had regression of thrombi, and there was no change in thrombus size in 68 patients (44%). Thrombus size increased in 3 patients (2%). Thrombosis was confirmed surgically and histopathologically in 12 patients (7%). In conclusion, real-time 3D TEE can detect prosthetic mitral ring thrombosis that could be missed on 2D TEE and cause thromboembolic events.

Prosthetic heart valve obstruction: thrombolysis or surgical treatment?

Prosthetic valve thrombosis is a potentially life-threatening complication associated with high morbidity and mortality. Transthorasic and transoesophageal echocardiography play an important role to the diagnosis and provides incremental information about the optimal treatment strategy, while fluoroscopy and cardiac computed tomography may be of added value. Guidelines differ on whether surgical treatment or fibrinolysis should be the treatment of choice for the management of left-sided prosthetic valve thrombosis and these uncertainties underline the need for further prospective randomized controlled trials. Thrombus size, New York Heart Association functional class of the patient, the possible contraindications, the availability of each therapeutic option and the clinician's experience are important determinants for the management of prosthetic valve thrombosis.

Successful thrombolytic treatment of prosthetic mitral valve thrombosis

Prosthetic heart valve thrombosis is a rare but serious complication. Surgery is the first-line therapy in symptomatic obstructive mechanical valve thrombosis, thrombolytic therapy has been used as an alternative to surgical treatment. In this case report we described a 47-year-old woman who had undergone coronary artery bypass graft and mitral valve replacement operation 9 months ago. A thrombus was detected on the prosthetic mitral valve with high transmitral gradient by transoesophageal echocardiography. Tissue plasminogen activator treatment was administered successfully. The gradient was improved on prosthetic mitral valve and embolic complications or bleeding were not occurred.

Effect of electrical stimulus parameters on the development and propagation of action potentials in short excitable fibres

Intracellular action potentials (IAPs) produced by short fibres in response to their electrical stimulation were analysed. IAPs were calculated on the basis of the Hodgkin-Huxley (1952) model by the method described by Joyner et al. (1978). Principal differences were found in processes of activation of short (semilength L less than 5 lambda) and long fibres under near-threshold stimulation. The shorter the fibre, the lower was the threshold value (Ithr). Dependence of the latency on the stimulus strength (Ist) was substantially non-linear and was affected by the fibre length. Both fibre length and stimulus strength influenced the IAP amplitude, the instantaneous propagation velocity (IPV) and the site of the first origin of the IAP (and, consequently, excitability of the short fibre membrane). With L less than or equal to 2 lambda and Ithr less than or equal to Ist less than or equal to 1.1Ithr, IPV could reach either very high values (so that all the fibre membrane fired practically simultaneously) or even negative values. The latter corresponded to the first origin of the propagated IAP, not at the site of stimulation but at the fibre termination or at a midpoint. The characters of all the above dependencies were unchanged irrespective of the manner of approaching threshold (variation of stimulus duration or its strength). Reasons for differences in processes of activation of short and long fibres are discussed in terms of electrical load and latency. Applications of the results to explain an increased jitter, velocity recovery function and velocity-diameter relationship are also discussed.